Batteries and other electrical energy storage devices have become widely used in not only military, space, and commercial applications but also in domestic applications. Therefore, it has become even more important to be able to efficiently and effectively obtain an accurate estimation of the battery's state-of-health. While voltage, current, and temperature may be used to gauge the remaining capacity of a battery, in critical applications it is also necessary to know impedance and power capability to get an accurate picture of battery health. Ideally, any measurement of battery health is done in-situ and has minimal impact on the battery. A great deal of work has been conducted to test battery impedance without effecting battery status. This work is documented in, for example, U.S. Pat. Nos. 7,688,036; 7,395,163 B1; 7,675,293 B2; 8,150,643 B1; 8,352,204 B2; 8,762,109 B2; 8,868,363 B2; and 9,244,130 B2, and U.S. Published Patent Application Nos. 2011/0270559 A1; 2014/0358462 A1; and 2017/0003354 A1. Each variation of the methods described in these documents improve the process of assessing battery health by, for example, increasing resolution. Recently, a method for testing battery impedance has been described that increases the resolution of a known system by a factor of ten. Key features of this high resolution method involve a new algorithm, auto-ranging to obtain the optimum level of excitation current, and increased preamplifier gain. The method also required an additional measurement channel that captures time records of the Sum-Of-Sines (SOS) current in addition to the SOS voltage from the test battery.
Although the above-methods have refined this important process, an improved method for calibration that will greatly simplify the calibration process and eliminate the extra measurement channel needed for some methods is still needed.
All patents, patent applications, provisional patent applications and publications referred to or cited herein, are incorporated by reference in their entirety to the extent they are not inconsistent with the teachings of the specification.